Study of the Effect of Physicochemical Degradation and Contamination of Motor Oils on Their Lubricity

Abstract

Internal combustion engine lubrication is essential for unwanted energy and material losses. As part of the experimental work, the lubricity of both new and worn motor oils of Society of Automotive Engineers (SAE) 15W-40 and SAE 10W-40 with different American Petroleum Institute (API) performance classifications, which were taken from various motor trains during maintenance or oil change, was assessed. A total of sixteen lubricant samples were evaluated. Lubricity, i.e., the load capacity of the lubricating film, was evaluated on the basis of the Reichert test. Viscosity, as one of the most important parameters of lubricants, was evaluated by the Stabinger Viscometer. Chemical degradation of motor oils (oxidation, nitration, sulfation), contamination of oils with fuel, soot, water, and loss of antioxidant zinc dialkyldithiophosphate (ZDDP) were monitored by Fourier-transform infrared (FTIR) spectroscopy. Of the fresh motor oils, OMV 10W-40 API SL/CF motor oil had the best lubricity. URANIA LD 15W-40 API CI-4 and M7ADS V 15W-40 API CI-4 CH-4/SL oils showed similar lubricity. M7ADS III 15W-40 API CF-4/SG motor oil showed the highest wear of wear surface, i.e., the lowest lubricity, of the tested new motor oils. Correlation analysis of the experimental data confirmed that the fuel content penetrated the motor oils significantly negatively correlates with the viscosity (R = −0.87). The low water contamination in motor oil does not cause a significant negative effect on lubricity. A significant correlation between the oxidation, nitration, and sulfation products of chemical degradation of the tested oils was confirmed (R ≥ 0.90). These degradation products improve lubricity due to their polarity, i.e., they have caused better lubricity of worn oils compared to new motor oils. Even the depletion of the antioxidant ZDDP did not affect the reduction in lubricity and anti-abrasion properties of chemically degraded motor oils. The experimental results of testing of worn motor oils taken from motor trains showed that current motor oils have excellent lubricity, which they maintain throughout their life.

Changes in the Key Physicochemical Parameters and Selected Trace Elements of Oil Due to Its Use in Hydraulic System of Woodworking Equipment

“…RSTW II samples also contained an abnormal to critical number of resins, which alerted to a high level of thermal degradation. A similar topic was also addressed by Hönig et al (2020) and Sejkorová et al (2021) who also assessed the condition of oils in tractors using infrared spectroscopy.…”

Application of FTIR-ATR Spectrometry in Conjunction with Multivariate Regression Methods for Viscosity Prediction of Worn-Out Motor Oils

“…The change in viscosity was apparently not affected by soot contamination of motor oil, which is reflected in an overall shift of the spectrum to higher absorbances in the region of about 2000 cm −1 ; this spectral region did not significantly correlate with the change in kinematic viscosity. A correlation of R = 0.34 between KV 100 • C and soot in worn-out motor oils operated in large-volume diesel engines was published in [55].…”

Atmospheric pressure matrix‐assisted laser desorption/ionization mass spectrometry of engine oil additive components

“…The composition of these tribofilms has been extensively investigated by various measurement techniques, such as X-ray photoelectron spectroscopy (XPS), 8,[10][11][12][13] X-ray absorption spectroscopy, [14][15][16] and transmission electron microscopy (TEM) combined with focused ion beam (FIB) cutting. 17 Other available techniques include X-ray absorption near edge structure (XANES), 16,18 RAMAN spectroscopy, 19 scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), 8,[20][21][22] Fourier-transform infrared (FTIR) spectroscopy, 23,24 electrospray ionization mass spectrometry (ESI-MS), 25,26 high-field asymmetric waveform ion mobility spectrometry coupled with mass spectrometry (FAIMS-MS), 27 or dynamic time-of-flight secondary ion mass spectrometry (TOF-SIMS). 28 Direct surface analysis techniques such as desorption electrospray ionization (DESI-MS) 29 oil analysis and direct analysis in real time coupled with mass spectrometry (DART-MS) 30 have been applied for quantitative analysis of a commercial lubricant antioxidant additive in a base oil, while mass spectrometric imaging (MSI) by means of laser desorption/ionization reflectron time-of-flight mass spectrometry (LDI-RTOF-MS) was used to analyse ex situ oil components applied as lubricant additives in a tribological layer of a tribologically stressed surface.…”

“…The composition of these tribofilms has been extensively investigated by various measurement techniques, such as X‐ray photoelectron spectroscopy (XPS), 8 , 10 , 11 , 12 , 13 X‐ray absorption spectroscopy, 14 , 15 , 16 and transmission electron microscopy (TEM) combined with focused ion beam (FIB) cutting. 17 Other available techniques include X‐ray absorption near edge structure (XANES), 16 , 18 RAMAN spectroscopy, 19 scanning electron microscopy (SEM) with energy‐dispersive X‐ray spectroscopy (EDS), 20 , 21 , 22 Fourier‐transform infrared (FTIR) spectroscopy, 23 , 24 electrospray ionization mass spectrometry (ESI‐MS), 25 , 26 high‐field asymmetric waveform ion mobility spectrometry coupled with mass spectrometry (FAIMS‐MS), 27 or dynamic time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS). 28 …”